Nano-powders are single or multi-phase polycrystals comprises particles with sizes of 1 to 100 nm in at least one direction. Various methods were suggested in the literature for the production of well-defined nano-powders. Some of them, such as presented in U.S. Pat. No. 6,312,643 to Upadhya et al. are respectively tedious and costly operation, comprises no less then 21 steps, treating the material in all solid, liquid and gas phases; wherein gas is evacuated from one processing chamber to less then 10−3 Torr, and then pressed in another processing chamber to at least 103 psi, heated to some 550° C. etc.
U.S. Pat. No. 6,054,495 to Markowitz et al. presents a powder of un-agglomerated metallic particles, made by making at least four dispersions of surfactants vesicles in the presence of metal ions, and then freeze-drying the obtained lipid phase. This costly method requires the operator to continuously control this very delicate, inflammable, multi-phase and complicated system, decreasing its compatibility with full-scale operations.
U.S. Pat. 5,476,535 to the applicant present a method for the production of nano-powders, especially of silver. This process comprising the steps of (a) forming an aluminum-silver alloy of a specific blend composition; (b) leaching the aluminum ingredient by a series of consequent leaching steps wherein a fresh leaching agent is reacting the treated solid material, providing a gradually porous and homogeneous silver alloy. Ultrasonic oscillations are applied in step (c), disintegrating the agglomerate and enhancing the penetration of the leaching agent into the ever growing porous of the alloy by the application of a plurality of ultrasonic oscillations. The leaching agent is leaving silver agglomerate in step (d), and then the agglomerate is washed and dried in a final step.
According to U.S. Pat. No. 6,012,658 to the applicant, the very same process was used as is to form metal flasks. Thus, the following two main steps were introduced: comminuting the alloys obtained by the aforementioned U.S. Pat. No. 5,476,535 into defined particles, and then faltering the obtained particles into strip-like highly porous alloys of predetermined characteristics.
Thus, there exists a need for cost-effective, simple process customizable for full-scale production of metallic nano-powders and to the valuable products produced thereof.